Neighbour's power tools tripping my RCD?

[JohnW2]

I typed a bit too slowly but, as you will see, I've just made that point as well!

Maybe it would be a better solution to have a 30mA time delayed RCD, rather than 100mA unit

Sure, as I've said before, and 'even better' (from all points of view other than 'division of circuits') if it wasn't even time-delayed! An upstream 30mA RCD represents the ideal 'braces' to go with the 'belt' of a downstream 30mA one. However, if there's already a 100mA time-delayed one there, I certainly see no reason to remove it (if it's not being replaced by a 30mA one)!

As a matter of practicality, I'm not at all sure that 30mA TD RCDS are easily (if at all) findable!

Kind Regards, John

 

[JohnW2]

Is there an official definition of 'nuisance tripping' as opposed to 'real'?

I guess I asked for that one I suppose I was talking about a real, and not 'very transient', single fault that was resulting in an L-N imbalance >30mA - but that's not a particularly good definition, either!

Kind Regards, John

 

[ceecjc1]

Wow, great response, thanks guys!

So it sounds like the RCD is possibly faulty and the neighbour is off the hook, but whatever the cause we need to get an electrician to take a look to diagnose the fault. The house is rented and we already reported the problem to the agents but they didn't offer to send anyone round. I will get back in touch with them and request them to get their electrician on the job.

Thanks!
Chris

 

[EFLImpudence]

I guess I asked for that one I suppose I was talking about a real, and not 'very transient', single fault that was resulting in an L-N imbalance >30mA - but that's not a particularly good definition, either!

I wasn't being awkward.

It's just that often people talk about 'nuisance tripping' as if it is something that is different (than a 'proper fault') and can be avoided.

For example, to prevent the RCCB tripping because of unknown faults, fit RCBOs.
This is obviously alright for a lot of 'leaky' equipment but not for faulty circuits.

 

[JohnW2]

I wasn't being awkward. ... It's just that often people talk about 'nuisance tripping' as if it is something that is different (than a 'proper fault') and can be avoided. ... For example, to prevent the RCCB tripping because of unknown faults, fit RCBOs. ... This is obviously alright for a lot of 'leaky' equipment but not for faulty circuits.

That'd really exactly the distinction I had in my mind. If there are N loads, each with small earth leaks which, together, add up to just over 30mA (or whatever the actual threshold happens to be) then one can have any combination of (N-1) of them on and there will be no trip, but switching on the Nth one (which, on different occasions, could be any of them) will result in a trip, even though there are no 'faults' anywhere. That I would call a 'nuisance' ('non-fault') trip. As I said, whilst that can happen with a 30mA RCD, it's far less likely with a 100mA one, making it more likely that a 100mA trip is due to a 'real fault' (or a faulty, trigger happy', RCD). Does that make sense?

Kind Regards, John

 

[WellKnownSid]

There are usually one or two components inside an RCD which help prevent nuisance tripping - these can sometimes fail (or they forget to fit them on the production line ) which results in the fault you describe...

Are there? What are they then?

Filtering capacitors, for a start - assuming that it's an electrically-triggered RCD.

Kind Regards, John

Usually nothing more complicated than an R/C circuit - possibly a capacitor to clamp the gate of the SCR, depending on the chip doing the processing.

A couple of decades ago I had a sideline designing some of the electronics for a well-known brand of RCD. IIRC the Raytheon RV4141 chip that they were using had a lower power consumption, but was more prone to nuisance tripping than the older RV4140. The problem was that the chip was designed for the lower US voltage - being intended for US-of-A style GFCI's - so the design of dropper was a little more critical at 230 (then 240) volts.

 

[JohnW2]

Usually nothing more complicated than an R/C circuit - possibly a capacitor to clamp the gate of the SCR, depending on the chip doing the processing. A couple of decades ago I had a sideline designing some of the electronics for a well-known brand of RCD. IIRC the Raytheon RV4141 chip that they were using had a lower power consumption, but was more prone to nuisance tripping than the older RV4140. The problem was that the chip was designed for the lower US voltage - being intended for US-of-A style GFCI's - so the design of dropper was a little more critical at 230 (then 240) volts.

That all makes sense. However, I would presume that a sufficiently large transient pulse, or even RF pick-up, would be able to defeat any attempts at immunising the RCD electronics against such things, wouldn't it?

Kind Regards, John

 

[EFLImpudence]

There are usually one or two components inside an RCD which help prevent nuisance tripping

Perhaps I should have posed my question under this quote.

By 'nuisance tripping' do you mean when it should not, i.e. due to the device malfunctioning?

 

[ban-all-sheds]

Back to the plot...

I'm a tad confused....

I've had a read through the forum and the answer to my question seems to be "yes",
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Is it possible that his power tools are causing my RCD to trip?
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So, my question to all of you experts is: could the neighbour be tripping my RCD

You've clearly got problems going on, and that's been discussed, but where have you read that the answer to this one of your questions is "yes"?

 

[JohnW2]

There are usually one or two components inside an RCD which help prevent nuisance tripping

Perhaps I should have posed my question under this quote. ... By 'nuisance tripping' do you mean when it should not, i.e. due to the device malfunctioning?

I know this wasn't directed at me, but it makes me realise that I should have added this to my previous answer to you ... I would personally regard an RCD trip as the result of 'device malfunction' (due to design/characteristic issues, not a 'fault'), in the absence of enough L-N imbalance to cause an 'intended' trip, as probably being the 'purest' example of 'nuisance tripping'.

I've got quite a few RCDs in my house (in an area in which there are a lot of overhead supplies) and, until a few years ago, it was common for one or more of them to trip whenever there were flashes of lightning within a few miles. It doesn't seem to happen any more (and I haven't changed the RCDs), so I wonder if the DNO has perhaps found a way of getting rid of some of the worst 'spikes' within their network?

Kind Regards, John

 

[ban-all-sheds]

I've got quite a few RCDs in my house (in an area in which there are a lot of overhead supplies) and, until a few years ago, it was common for one or more of them to trip whenever there were flashes of lightning within a few miles.

Not as bad as the old VOELCBs in that respect...

 

[pjcomp]

RCD trips don't necessarily respond to faults inside the property - they can be caused from outside, particularly when overhead supplies are involved. I've known two occasions where this was the case - each time the DNO came and had a look at the pole connections, denied it was anything to do with them .... but the tripping stopped happening anyway.

In this case, as the 100mA RCD is tripping, doesn't it make more sense that the fault current is coming fro outside and hitting the 100mA RCD first rather than creating complex scenarios in which two 30mA RCDs fail together?

This doesn't necessarily mean that the neighbour's power tools are involved, nor does it let the neighbour off the hook. Does each house get a separate supply cable from the pole outside, or does it come to one house then daisy-chain across to the next one? If the latter there could be some spillover between properties. The OP says the neighbour's RCD doesn't trip - is he sure the neighbour has an RCD?

PJ

 

[JohnW2]

I've got quite a few RCDs in my house (in an area in which there are a lot of overhead supplies) and, until a few years ago, it was common for one or more of them to trip whenever there were flashes of lightning within a few miles.

Not as bad as the old VOELCBs in that respect...

Interesting - but I find that difficult to understand, unless there were some 'late' VOELCBs which used electronic sensing/tripping. The VOELCBs I know have al been purely electromechanical, and it's difficult to see how very short duration 'spikes' could make them operate.

Kind Regards, John

 

[JohnW2]

In this case, as the 100mA RCD is tripping, doesn't it make more sense that the fault current is coming fro outside and hitting the 100mA RCD first rather than creating complex scenarios in which two 30mA RCDs fail together?

If it were a 'fault current' in the normal sense, that could not be the case, because the nature of electrical circuits is such that the same currents would flow through the 100mA RCD and at least one of the 30mA ones. However, 'false triggering' of the electronics of the 100mA RCD by voltage spikes on the supply could possibly be the explanation.

The 'complex situation' obviously would not require both 30mA RCDs to have failed. If, for example (as has been suggested as a possibility), the OP's dishwasher has an intermittent fault, then failure of just the one 30mA RCD serving that appliance would (if fault current was >100mA) result in trips of the 100mA one.

Kind Regards, John

 

[JohnW2]

The RCD in my house tripped repeatedly today (4-5 times per session) when the neighbour was sanding his floors using some kind of power tool. ..... The RCD had been tripping occasionally (once or twice a week) over the last few weeks while the dishwasher was on .... Note that the 30mA RCDs do not trip and it's the 100mA one which always needs reset.

Although I realise that it has been agreed that you need to get an electrician to investigate all this, it has occurred to me that (in terms of our detective work/speculation) there are a couple of fairly crucial questions that none of us have asked you ...

Firstly, as regards the trips you have been experiencing in recent weeks when the dishwasher was on, were these trips also always of the 100mA RCD, with no 30mA one ever tripping? Secondly, do I take it that your dishwasher was not on when you experienced the trips whilst your neighbour was sanding?

Kind Regards, John